Industrial sheet metal cabinets often have doors which are maintained in closed position by a latch assembly mounted on the moveable door and arranged to engage a lip on the stationary cabinet frame. When such cabinets are used to house electrical equipment, it is often highly desirable or required from a safety standpoint that all parts of the cabinet, including the latch assembly and the handle grasped by the user, be electrically grounded. Additionally, cabinets including but not limited to those made of sheet metal are made in a wide variety of sizes and door configurations and it is highly desirable that the cabinet latch assembly include certain universal mounting features so that the assembly may be adapted to cabinets of variant types.
One approach to the attachment of a lock assembly to a sheet metal cabinet door is by the use of a threaded shank on the assembly which is inserted from one side of the door through an aperture and a nut is thereupon affixed to the protruding shank at the opposite side of the door. With grounded electrical cabinets, a disadvantage of an assembly of this type is that, of necessity, the aperture must be slightly larger than the threaded shank and no electrical contact occurs. Even though a nut may be affixed, its smooth face which bears against the non-conductive surface coating, paint for example, is incapable of reliably piercing the coating to provide good electrical grounding.
Another approach to the attachment of latch assemblies is by screws inserted through holes other than the main aperture in which the assembly is received. The screw holes are located in such a way as to be in a register with threaded holes in the assembly and the screws are merely passed through the holes in the door and tightened to the assembly. This type of assembly suffers from some of the same deficiencies as that described above in that the aperture must necessarily be sized to provide some clearance for the inserted assembly. Similarly, the screw holes must be sized with a degree of clearance and the screws may not reliably pierce the non-conducting coating.
A latch assembly which would reliably pierce non-conducting coatings upon sheet metal doors and which also has universal mounting characteristics would be an important advance in the art.